<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1, .box2{
            width:100px;
            height:100px;
        }
        h1{
            color:red
        }
        .myh1{
            color:aqua
        }
        div div{
            color:red
        }
        div .mydiv{
            color:blueviolet
        }
        div p{
            color:brown
        }
        #myid{
            color:red
        }
        .box1{
            background-color: red;
        }
        .box2{
            background-color: blue;
        }

        .box3{
            width:100px;
            height: 100px;
            background-color: red;
        }
        .box3:hover{
            width: 200px;
            height: 200px;
            background-color: blue;
        }
    </style>
    
</head>
<body>
    <h1>english</h1>

    <h1 class="myh1">american</h1>

    <div>
        <div>jiay</div>
        <div class="mydiv">yyy</div>
        <div>
            <p>船只</p>
        </div>
    </div>

    <div>hoooo</div>

    <div id=myid>itcast</div>
    
    <div class="box1"></div>
    <div class="box2"></div>
    <div class="box3"></div>
</body>
</html>